JP7157171B2 - core, stator, and rotating electrical machine - Google Patents

Description

The present disclosure relates to cores, stators, and rotating electric machines.
This application claims priority based on Japanese Patent Application No. 2018-202373 dated October 26, 2018, and incorporates all the descriptions described in the Japanese application.

Patent Documents 1 and 2 disclose an axial gap type motor (rotating electrical machine) in which a rotor and a stator are arranged to face each other in the axial direction. A stator used in this type of rotating electrical machine includes a core having an annular back yoke, a plurality of teeth projecting axially from the back yoke, and coils arranged on each tooth. A plurality of teeth are provided on one surface (upper surface) of the back yoke at intervals in the circumferential direction.

Patent Literature 1 describes that the core is made of a compacted body in which a back yoke and teeth are integrally molded.

JP 2009-142095 A JP 2017-229191 A

The core of this disclosure is
A core used in an axial gap type rotating electric machine,
an annular back yoke;
a plurality of teeth protruding in an axial direction perpendicular to the first plane of the back yoke,
The plurality of teeth are provided at intervals in the circumferential direction of the first plane,
The back yoke and the teeth are formed of an integrally molded compacted body,
a first curved surface portion connecting between the peripheral surface of the tooth and the first flat surface of the back yoke at a corner portion between the tooth and the back yoke;
A radius of curvature of the first curved surface portion is 0.2 mm or more and 1.5 mm or less.

The stator of the present disclosure is
A stator for an axial gap type rotary electric machine,
the core of the present disclosure;
a coil arranged on each tooth of the core.

The rotating electric machine of the present disclosure is
An axial gap type rotary electric machine comprising a rotor and a stator, wherein the rotor and the stator are arranged to face each other in an axial direction,
The stator is the stator of the present disclosure.

1 is a schematic top view of a core according to an embodiment; FIG. FIG. 2 is a schematic cross-sectional view along line II-II of FIG. 3 is a partially enlarged schematic sectional view of FIG. 2. FIG. FIG. 4 is a schematic cross-sectional view showing an example of a mold for molding the core according to the embodiment. FIG. 5 is a schematic top view of the die. FIG. 6 is a schematic cross-sectional view along line VI-VI of FIG. 7 is a partially enlarged schematic sectional view of FIG. 6. FIG. FIG. 8 is a schematic top view of the lower punch. 9 is a schematic cross-sectional view along line IX-IX of FIG. 8. FIG. FIG. 10 is a partially enlarged schematic cross-sectional view showing a state in which the core is molded with a mold. FIG. 11 is a schematic top view of the stator according to the embodiment. FIG. 12 is a schematic cross-sectional view of the rotating electric machine according to the embodiment. FIG. 13A is a schematic top view showing an example of a core according to a modification; FIG. 13B is a schematic cross-sectional view of a rotating electric machine using the core shown in FIG. 13A. FIG. 14A is a schematic top view showing another example of a core according to a modification; FIG. 14B is a schematic cross-sectional view of a rotating electrical machine using the core shown in FIG. 14A.

[Problems to be Solved by the Present Disclosure]
It is desired to improve the efficiency of an axial gap type rotating electric machine. From the viewpoint of improving the efficiency of rotating electric machines, it is desirable to improve the magnetic properties of cores used in rotating electric machines.

One object of the present disclosure is to provide a core capable of improving magnetic properties. Another object of the present disclosure is to provide a stator including the core. Further, another object of the present disclosure is to provide a rotating electric machine including the stator.

[Effect of the present disclosure]
The core of the present disclosure can have improved magnetic properties. Also, the stator of the present disclosure has excellent core magnetic properties. Furthermore, the rotating electric machine of the present disclosure is highly efficient.

[Description of Embodiments of the Present Disclosure]
The present inventors have made intensive studies on the magnetic properties of cores used in axial gap type rotating electric machines, and have obtained the following findings.

2. Description of the Related Art In an axial gap type rotating electrical machine, when a current is passed through a coil, magnetic flux flows through the core and a magnetic path is formed. When the magnetic flux flowing through the core decreases, the torque of the rotating electrical machine decreases. In the core of the rotary electric machine, magnetic flux flows axially through the teeth, and magnetic flux flows circumferentially through the back yoke. Therefore, the direction of magnetic flux changes between the teeth and the back yoke.

As described in Patent Document 2, in a core made of a conventional compacted body, two lower punches are used when molding using a mold, and the end surfaces of the teeth and the back yoke from which the teeth protrude are cut. It is common to form the first plane with different lower punches. In this case, from the viewpoint of punch strength, etc., the teeth are molded so that the peripheral surfaces of the teeth and the first plane of the back yoke from which the teeth protrude are perpendicular to each other. In such a core, since the circumferential surface of the teeth and the first plane of the back yoke are perpendicular to each other, when the magnetic flux flows through the corners between the teeth and the back yoke, part of the magnetic flux passes through the outside of the core. A shortcut may be formed between the circumferential surface of the tooth and the first plane of the back yoke. That is, leakage magnetic flux is likely to occur at the corners of the teeth and the back yoke. If leakage magnetic flux is generated in the core of the rotating electric machine, it will lead to a decrease in torque and an increase in loss in the core, leading to a decrease in efficiency.

The present inventors attempted to use a stepped die to form the end faces of the teeth with a lower punch and the first plane of the back yoke with the die. As a result, the first curved surface portion can be formed at the corners of the teeth and the back yoke, and the core leakage magnetic flux generated at the corners of the teeth and the back yoke can be reduced compared to the above-described conventional core. Found it. This is because the formation of the first curved surface portions at the corners of the teeth and the back yoke reduces leakage magnetic flux that shortcuts between the circumferential surfaces of the teeth and the first plane of the back yoke. By using the core having the first curved surface portions at the corners of the teeth and the back yoke in the axial gap type rotary electric machine, it is possible to suppress torque reduction and core loss due to leakage magnetic flux. Therefore, by having the first curved surface portion, the magnetic properties of the core can be improved, and the efficiency of the rotating electric machine can be improved.

The present disclosure is made based on the above findings. First, the embodiments of the present disclosure are listed and described.

(1) The core according to an embodiment of the present disclosure is
A core used in an axial gap type rotating electric machine,
an annular back yoke;
a plurality of teeth protruding in an axial direction perpendicular to the first plane of the back yoke,
The plurality of teeth are provided at intervals in the circumferential direction of the first plane,
The back yoke and the teeth are formed of an integrally molded compacted body,
a first curved surface portion connecting between the peripheral surface of the tooth and the first flat surface of the back yoke at a corner portion between the tooth and the back yoke;
A radius of curvature of the first curved surface portion is 0.2 mm or more and 1.5 mm or less.

Since the core of the present disclosure has the first curved surface portions at the corners of the teeth and the back yoke, it is possible to reduce leakage magnetic flux generated at the corners of the teeth and the back yoke. Therefore, the core can have improved magnetic properties. Leakage magnetic flux can be effectively reduced by setting the radius of curvature of the first curved surface portion to 0.2 mm or more. In addition, since the radius of curvature of the first curved surface portion is 1.5 mm or less, it is possible to secure space for the coils arranged on the teeth and improve the space factor of the coils. As a result, a decrease in the number of turns of the coil can be suppressed, so a decrease in the torque of the rotating electric machine can be suppressed.

(2) As one form of the core,
an outer curved surface portion connecting between the first plane and the outer peripheral surface of the back yoke;
an inner curved surface portion connecting between the first plane and the inner peripheral surface of the back yoke,
Each radius of curvature of the outer curved surface portion and the inner curved surface portion may be 0.5 mm or more.

The core made of the powder compact is formed by compressing the soft magnetic powder with a mold. Specifically, the teeth may be formed with a lower punch and the back yoke with a die. Bending stress tends to concentrate on the corners of the mold, particularly the die, due to the molding pressure when the core is molded using the mold, and cracks may occur in the corners of the mold. In the above embodiment, the radius of curvature of each of the outer curved surface portion and the inner curved surface portion of the back yoke is 0.5 mm or more, so that stress concentration at the corners of the mold can be alleviated. Therefore, the above configuration can suppress damage to the mold. Although the upper limit of each radius of curvature of the outer curved surface portion and the inner curved surface portion is not particularly limited, it may be, for example, 5.0 mm or less. As the radius of curvature of each of the outer curved surface portion and the inner curved surface portion increases, the length of the straight portions of the outer peripheral surface and the inner peripheral surface of the back yoke becomes shorter than the thickness of the back yoke. If the radius of curvature of each of the outer curved surface portion and the inner curved surface portion is 5.0 mm or less, it is easy to secure the length of the straight portions of the outer peripheral surface and the inner peripheral surface of the back yoke.

(3) As one form of the core described in (2) above,
The radius of curvature of the outer curved surface portion and the radius of curvature of the inner curved surface portion may be different.

The radii of curvature of the outer curved surface portion and the inner curved surface portion of the back yoke may be different. When the outer curved surface portion and the inner curved surface portion have different curvature radii, it is preferable that the outer curved surface portion has a larger curvature radius than the inner curved surface portion. When molding the core using a mold, the outer corner of the mold that forms the corner of the outer peripheral edge of the back yoke is closer to the inner corner of the mold that forms the corner of the inner peripheral edge of the back yoke. stress tends to be higher. When the radius of curvature of the outer curved surface portion is larger than the radius of curvature of the inner curved surface portion, stress concentration at the outer edge corners of the mold can be effectively alleviated. Therefore, the above-mentioned form tends to suppress damage to the mold. When a rotating electric machine is constructed using the above core, magnetic flux tends to flow more easily on the inner peripheral side of the back yoke than on the outer peripheral side. Since the radius of curvature of the outer curved surface portion is larger than the radius of curvature of the inner curved surface portion, it becomes easier to ensure the effective magnetic path area of the back yoke. As a result, it is possible to suppress the concentration of the magnetic flux on the inner peripheral side of the back yoke, which is expected to have the effect of improving the torque and efficiency of the rotary electric machine.

(4) As one form of the core,
At least one of the outer peripheral surface and the inner peripheral surface of the back yoke has a linear portion extending along the axial direction,
The length of the linear portion may be 15% or more of the thickness of the back yoke.

When the core is housed in a case to form a rotating electric machine, the outer peripheral surface of the back yoke may be fitted to the inner peripheral surface of the case. When the back yoke has a straight portion on the outer peripheral surface, the straight portion on the outer peripheral surface comes into surface contact with the inner peripheral surface of the case, thereby facilitating fixing of the core to the case. Further, when a rotating electric machine is configured using the core, a bus bar for connecting coils may be attached inside the back yoke. When the inner peripheral surface of the back yoke has a straight portion, the straight portion of the inner peripheral surface comes into surface contact with the busbar, making it easier to fix the busbar to the core. In the above embodiment, the length of the linear portion of at least one of the outer peripheral surface and the inner peripheral surface of the back yoke is 15% or more of the thickness of the back yoke. The upper limit of the ratio of the length of the linear portion to the thickness of the back yoke on the outer and inner peripheral surfaces of the back yoke is not particularly limited, but may be, for example, 75% or less of the thickness of the back yoke. The length of the linear portion is, for example, 0.5 mm or more and 9 mm or less. The thickness of the back yoke is, for example, 1.5 mm or more and 10 mm or less.

(5) As one form of the core,
The difference between the radial dimension from the axial center of the back yoke to the outer peripheral surface and the radial dimension from the axial center of the back yoke to the outer peripheral surface of the tooth is 6.0 mm or less. is mentioned.

In the back yoke, the area from the outer peripheral surface of the back yoke to the portion where the teeth protrude is defined as the outer peripheral area. When the molded core is removed from the mold, bending stress may act on the outer peripheral region of the back yoke. This stress may deform the peripheral region. The smaller the radial dimension of the outer peripheral region of the back yoke, the easier it is to suppress the deformation of the outer peripheral region due to the stress during removal from the mold. In the above embodiment, the difference between the radial dimension from the axial center of the back yoke to the outer peripheral surface and the radial dimension from the axial center of the back yoke to the surface located on the outer peripheral side of the tooth is 6.0 mm or less. . As a result, the radial dimension of the outer peripheral region of the back yoke is reduced, and deformation of the outer peripheral region can be suppressed. Hereinafter, the radial dimension from the axial center of the back yoke to the outer peripheral surface may be referred to as the "outer radius of the back yoke". The radial dimension from the axial center of the back yoke to the surface positioned on the outer peripheral side of the tooth is sometimes referred to as the "outer radius of the tooth."

Further, if the difference between the outer radius of the back yoke and the outer radius of the teeth is 6.0 mm or less, the compressed area when molding the core using a mold becomes small. Therefore, a high molding pressure can be applied, so that the density of the core can be increased. Further, the difference between the outer radius of the back yoke and the outer radius of the teeth is 4.0 mm or less and 3.0 mm or less.

(6) As one form of the core,
The difference between the radial dimension from the axial center of the back yoke to the surface positioned on the inner peripheral side of the tooth and the radial dimension from the axial center to the inner peripheral surface of the back yoke is 7.0 mm or less. There is one thing.

In the back yoke, the area from the inner peripheral surface of the back yoke to the portion where the teeth protrude is defined as the inner peripheral area. When the molded core is removed from the mold, bending stress may act on the inner peripheral region of the back yoke. This stress may deform the inner peripheral region. The smaller the radial dimension of the inner peripheral region of the back yoke, the easier it is to suppress the deformation of the inner peripheral region due to the stress during removal from the mold. In the above embodiment, the difference between the radial dimension from the axial center of the back yoke to the surface located on the inner peripheral side of the teeth and the radial dimension from the axial center of the back yoke to the inner peripheral surface is 7.0 mm or less. is. As a result, the radial dimension of the inner peripheral region of the back yoke is reduced, and deformation of the inner peripheral region can be suppressed. Hereinafter, the radial dimension from the axial center of the back yoke to the surface positioned on the inner peripheral side of the tooth may be referred to as the "inner radius of the tooth." The radial dimension from the axial center of the back yoke to the inner peripheral surface is sometimes referred to as the "inner radius of the back yoke".

Also, if the difference between the inner radius of the teeth and the inner radius of the back yoke is 7.0 mm or less, the compression area when molding the core using a die becomes small. Therefore, a high molding pressure can be applied, so that the density of the core can be increased. Further, the difference between the inner radius of the teeth and the inner radius of the back yoke is 5.0 mm or less and 4.0 mm or less.

(7) As one form of the core,
At least one of the outer peripheral surface and the inner peripheral surface of the back yoke may be partially provided with a radially projecting protrusion or a radially recessed recess.

When a rotating electrical machine is configured using the core, the above-described form has a convex portion or a concave portion on the outer peripheral surface of the back yoke, and the convex portion or the concave portion can be used for positioning with respect to the case. For example, a protrusion or a recess is provided on the outer peripheral surface of the back yoke, and a recess or protrusion corresponding to this protrusion or recess is provided on the inner peripheral surface of the case. It is possible to position the core with respect to the case by fitting these projections and recesses. Further, when a rotating electric machine is configured using the core, the bus bar may be arranged inside the back yoke. By providing the protrusion or recess on the inner peripheral surface of the back yoke, the protrusion or recess can be used for positioning the bus bar. For example, a protrusion or a recess is provided on the inner peripheral surface of the back yoke, and a recess or protrusion corresponding to this protrusion or recess is provided on the bus bar. It is possible to position the busbar with respect to the core by fitting the protrusions and recesses.

(8) As one form of the core,
The powder compact is composed of an aggregate of a plurality of coated soft magnetic particles having an insulating coating on the surface of the soft magnetic particles,
The soft magnetic particles are made of pure iron or at least one iron-based alloy selected from Fe—Si alloys, Fe—Al alloys, Fe—Cr—Al alloys and Fe—Cr—Si alloys. It is mentioned that they are iron-based particles.

Pure iron or the above iron-based alloys are relatively soft. Therefore, when the soft magnetic particles are iron-based particles made of pure iron or the iron-based alloy, the soft magnetic particles are easily deformed during molding of the powder compact. Therefore, in the above-described form, a powder compact with high density and high dimensional accuracy can be obtained. By increasing the density of the compact, the mechanical strength and magnetic properties of the core can be improved. Moreover, by having an insulating coating on the surface of the soft magnetic particles, the electrical insulation between the soft magnetic particles can be enhanced. Therefore, core iron loss caused by eddy current loss can be reduced.

(9) As one form of the core described in (8) above,
The insulating coating may include a phosphate coating.

Phosphate coating has high adhesion to iron-based particles and is excellent in deformability. Therefore, since the insulating coating contains the phosphate coating, it is easy to follow the deformation of the iron-based particles during the molding of the powder compact. Therefore, in the above configuration, the insulation coating is less likely to be damaged, and the iron loss of the core can be reduced.

(10) As one form of the core,
The relative density of the powder compact is 90% or more.

In the above-described mode, the relative density of the powder compact is 90% or more, so that the density of the compact is high. By increasing the density of the powder compact, the mechanical strength and magnetic properties of the core can be improved.

(11) The core according to embodiments of the present disclosure is
A core used in an axial gap type rotating electric machine,
an annular back yoke;
a plurality of teeth protruding in an axial direction perpendicular to the first plane of the back yoke,
The plurality of teeth are provided at intervals in the circumferential direction of the first plane,
The back yoke and the teeth are formed of an integrally molded compacted body,
a first curved surface portion connecting between the peripheral surface of the tooth and the first flat surface of the back yoke at a corner portion between the tooth and the back yoke;
The first curved surface portion has a radius of curvature of 0.2 mm or more and 1.5 mm or less,
an outer curved surface portion connecting between the first plane and the outer peripheral surface of the back yoke;
an inner curved surface portion connecting between the first plane and the inner peripheral surface of the back yoke,
Each curvature radius of the outer curved surface portion and the inner curved surface portion is 0.5 mm or more,
At least one of the outer peripheral surface and the inner peripheral surface of the back yoke has a linear portion extending along the axial direction,
The length of the linear portion is 15% or more of the thickness of the back yoke.

Since the core of the present disclosure has the first curved surface portions at the corners of the teeth and the back yoke, it is possible to reduce leakage magnetic flux generated at the corners of the teeth and the back yoke. Therefore, the core can have improved magnetic properties. In particular, when the radius of curvature of the first curved surface portion is 0.2 mm or more, leakage magnetic flux can be effectively reduced. In addition, since the radius of curvature of the first curved surface portion is 1.5 mm or less, it is possible to secure space for the coils arranged on the teeth and improve the space factor of the coils. As a result, a decrease in the number of turns of the coil can be suppressed, so a decrease in the torque of the rotating electric machine can be suppressed.

In addition, as described in the embodiment described in (2) above, the curvature radius of each of the outer curved surface portion and the inner curved surface portion of the back yoke is 0.5 mm or more, thereby relieving the stress concentration at the corners of the mold. can. Therefore, the core can suppress damage to the mold.

Furthermore, as described in the aspect (4) above, the length of the straight portion of at least one of the outer peripheral surface and the inner peripheral surface of the back yoke is 15% or more of the thickness of the back yoke, so that Assembly of a case and a bus bar becomes easy.

(12) A stator according to an embodiment of the present disclosure,
A stator for an axial gap type rotary electric machine,
The core according to any one of (1) to (11) above;
a coil arranged on each tooth of the core.

The stator has excellent core magnetic properties. This is because the magnetic properties of the core can be improved by providing the core according to the embodiment.

(13) A rotating electric machine according to an embodiment of the present disclosure includes:
An axial gap type rotary electric machine comprising a rotor and a stator, wherein the rotor and the stator are arranged to face each other in an axial direction,
The stator is the stator according to (12) above.

The rotating electric machine described above is highly efficient. This is because the magnetic properties of the core are excellent by providing the stator according to the embodiment.

[Details of the embodiment of the present disclosure]
Specific examples of a core, a stator, and a rotating electrical machine according to embodiments of the present disclosure will be described below with reference to the drawings. The same reference numerals in the drawings indicate the same names. The present invention is not limited to these exemplifications, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

<Core>
A core 1 according to an embodiment will be described with reference to FIGS. 1 to 3. FIG. The core 1 is used for an axial gap type rotary electric machine. A core 1 includes an annular back yoke 2 and a plurality of teeth 3 projecting from the back yoke 2 . One of the features of the core 1 is that it has a first curved surface portion 31 at the corner portion between the teeth 3 and the back yoke 2, as shown in FIGS. In the following description, when describing the core 1, the side from which the teeth 3 protrude is the top, and the opposite side is the bottom.

(back yoke)
The back yoke 2 shown in FIG. 1 has an annular plate shape. As shown in FIG. 2 , one plane of the back yoke 2 , that is, the upper surface is defined as a first plane 21 , and the surface opposite to the first plane 21 , that is, the lower surface is defined as a second plane 22 . On the first plane 21 of the back yoke 2, as shown in FIG. 2, teeth 3 are provided so as to protrude. The thickness of the back yoke 2 is, for example, 1.5 mm or more and 10 mm or less, and further 2.0 mm or more and 7.0 mm or less. In FIG. 2, the thickness of the back yoke 2 is indicated by T2. In this example, the first plane 21 and the second plane 22 are planes along the direction orthogonal to the axial direction of the back yoke 2 .

In the back yoke 2 , the corners of the outer peripheral edge of the first plane 21 have outer curved surface portions 23 that connect the first plane 21 and the outer peripheral surface of the back yoke 2 , as shown in FIG. 2 . The outer curved surface portion 23 is an arc inscribed with the extension surface of the first plane 21 and the outer peripheral surface of the back yoke 2, in other words, an arc convex toward the line of intersection of both extension surfaces. In addition, an inner curved surface portion 24 that connects the first flat surface 21 and the inner peripheral surface of the back yoke 2 is provided at a corner portion of the inner peripheral edge of the first plane 21 . The inner curved surface portion 24 is an arc inscribed with the extension surface of the first plane 21 and the inner peripheral surface of the back yoke 2, in other words, an arc convex toward the line of intersection of both extension surfaces. Each radius of curvature of the outer curved surface portion 23 and the inner curved surface portion 24 is preferably, for example, 0.5 mm or more, more preferably 1.0 mm or more, and more preferably 1.5 mm or more. The upper limit of each radius of curvature of the outer curved surface portion 23 and the inner curved surface portion 24 is, for example, 5.0 mm or less, further 4.0 mm or less, or 3.0 mm or less. The radius of curvature of each of the outer curved surface portion 23 and the inner curved surface portion 24 is, for example, preferably 10% or more and 85% or less, more preferably 20% or more and 60% or less, of the thickness of the back yoke 2 . The radius of curvature of the outer curved surface portion 23 and the radius of curvature of the inner curved surface portion 24 may be the same or different. In FIG. 2, the radius of curvature of the outer curved surface portion 23 and the radius of curvature of the inner curved surface portion 24 are the same.

When the radius of curvature of each of the outer curved surface portion 23 and the inner curved surface portion 24 is 0.5 mm or more, stress concentration at the corners of the mold can be alleviated when the core 1 is molded using the mold. Therefore, damage to the mold can be suppressed. The reason for this will be described later. Further, if the radius of curvature of each of the outer curved surface portion 23 and the inner curved surface portion 24 is 5.0 mm or less, the length of the straight portions 25 and 26 of the outer peripheral surface and the inner peripheral surface of the back yoke 2 can be easily secured. This is because when the radius of curvature of the outer curved surface portion 23 or the inner curved surface portion 24 is increased, the length of the straight portions 25 and 26 of the outer or inner peripheral surface becomes shorter than the thickness of the back yoke 2 .

When the outer curved surface portion 23 and the inner curved surface portion 24 have different curvature radii, it is preferable that the outer curved surface portion 23 has a larger curvature radius than the inner curved surface portion 24 . When molding the core 1 using a mold, the outer edge corner of the mold that forms the corner of the outer peripheral edge of the back yoke 2 is the inner edge angle of the mold that forms the corner of the inner peripheral edge of the back yoke 2. The stress tends to be higher than that of the part. When the radius of curvature of the outer curved surface portion 23 is larger than the radius of curvature of the inner curved surface portion 24, stress concentration at the outer edge corners of the mold can be effectively alleviated. Therefore, damage to the mold can be easily suppressed.

At least one of the outer peripheral surface and the inner peripheral surface of the back yoke 2 preferably has a linear portion extending along the axial direction. In this example, straight portions 25 and 26 are provided on the outer peripheral surface and the inner peripheral surface. The length of the linear portions 25 and 26 is preferably, for example, 15% or more of the thickness of the back yoke 2, and more preferably 25% or more.

When housing the core 1 in a case, the outer peripheral surface of the back yoke 2 may be fitted to the inner peripheral surface of the case. When the back yoke 2 has the straight portion 25 on the outer peripheral surface, the straight portion 25 comes into surface contact with the inner peripheral surface of the case, thereby making it easier to fix the core 1 to the case. Further, when a rotating electric machine is configured using the core 1 , a bus bar may be provided inside the back yoke 2 . When the back yoke 2 has the straight portion 26 on the inner peripheral surface, the straight portion 26 comes into surface contact with the busbar, thereby making it easier to fix the busbar to the core 1 . Since the length of the straight portions 25 and 26 is 15% or more of the thickness of the back yoke 2, it becomes easy to attach the case and the busbar to the core 1. The upper limit of the ratio of the lengths of the linear portions 25 and 26 to the thickness of the back yoke 2 is, for example, 90% or less of the thickness of the back yoke 2, and further 80% or less. The length of the linear portions 25 and 26 is, for example, 0.5 mm or more and 9 mm or less, and further 0.8 mm or more and 8.0 mm or less.

(teeth)
As shown in FIG. 1, the teeth 3 are provided on the first plane 21 of the back yoke 2 at intervals in the circumferential direction. The teeth 3 protrude from the first plane 21 in the axial direction of the back yoke 2, as shown in FIG. Specifically, the teeth 3 protrude in a direction perpendicular to the first plane 21 . The number of teeth 3 may be determined as appropriate, and is, for example, 3 or more, or 6 or more. In this example, as shown in FIG. 1, nine teeth 3 are arranged at regular intervals in the circumferential direction. Further, the shape of the teeth 3 is not particularly limited, and may be various shapes such as a columnar shape and a polygonal columnar shape. In this example, the tooth 3 has a triangular prism shape. The shape of the teeth 3 may be a quadrangular prism shape such as a trapezoidal prism shape.

2 and 3, the corners of the teeth 3 and the back yoke 2 have first curved surface portions 31 that connect the circumferential surfaces of the teeth 3 and the first flat surface 21 of the back yoke. The radius of curvature of the first curved surface portion 31 is 0.2 mm or more and 1.5 mm or less, preferably 0.3 mm or more, and further 0.4 mm or more and 1.2 mm or less. By having the first curved surface portion 31 , the root portion side of the tooth 3 connected to the back yoke 2 is formed such that the peripheral surface of the tooth 3 widens toward the first plane 21 . A portion of the peripheral surface of the tooth 3 other than the first curved surface portion 31 is formed linearly along the axial direction of the tooth 3 .

Coils 110 are arranged on the peripheral surfaces of the teeth 3 as shown in FIG. By applying a current to the coil 110, magnetic flux flows through the core 1 and a magnetic path is formed. Since the radius of curvature of the first curved surface portion 31 is 0.2 mm or more, the leakage magnetic flux generated at the corners between the teeth 3 and the back yoke 2 can be reduced. Moreover, since the radius of curvature of the first curved surface portion 31 is 1.5 mm or less, it is easy to secure a space for the coil 110 arranged on the teeth 3 . Therefore, reduction in the number of turns of the coil 110 can be suppressed.

In order to ensure electrical insulation between the core 1 and the coil 110, the surface of the core 1 may be coated with an insulating coating (not shown). The insulating coating film can be formed by applying an electrically insulating resin. Examples of the resin forming the insulating coating film include epoxy resin, fluorine resin, and polyimide resin. The insulating coating film may be provided at least on the surface of the core 1 that is in contact with the coil 110 . For example, the insulating coating film may be provided on the peripheral surfaces of the teeth 3 and the first flat surface 21 of the back yoke 2 . Also, an insulator (not shown) may be interposed between the core 1 and the coil 110 .

In the core 1, the difference between the outer radius of the back yoke 2 and the outer radius of the teeth 3 is preferably 0 mm or more and 6.0 mm or less, more preferably 4.0 mm or less and 3.0 mm or less. The outer radius of the back yoke 2 means the radial dimension from the axial center of the back yoke 2 to the outer peripheral surface. The outer radius of the teeth 3 means the radial dimension from the axial center of the back yoke 2 to the surface of the teeth 3 located on the outer peripheral side. In FIG. 1, the outer radius of the back yoke 2 is indicated by R2o, and the outer radius of the teeth 3 is indicated by R3o. When the difference (R2o-R3o) between the outer radius of the back yoke 2 and the outer radius of the teeth 3 is 6.0 mm or less, as shown in FIG. become smaller. The outer peripheral region 27 of the back yoke 2 refers to the region from the outer peripheral surface of the back yoke 2 to the portion where the teeth 3 protrude. As the radial dimension of the outer peripheral region 27 of the back yoke 2 is smaller, the bending stress acting on the outer peripheral region 27 can be reduced when the molded core 1 is removed from the mold. The reason for this will be described later. Therefore, if the difference between the outer radius R2o of the back yoke 2 and the outer radius R3o of the teeth 3 is 6.0 mm or less, and further 4.0 mm or less, the deformation of the outer peripheral region 27 due to the stress when removing from the mold is suppressed. can.

Further, when the difference between the outer radius R2o of the back yoke 2 and the outer radius R3o of the teeth 3 is 6.0 mm or less, and further 3.0 mm or less, the compression area when molding the core using a mold becomes small. . Therefore, since high molding pressure can be applied, the density of the core 1 can be increased. The reason for this will be described later.

In the core 1, the difference between the inner radius of the teeth 3 and the inner radius of the back yoke 2 is preferably 0 mm or more and 7.0 mm or less, more preferably 5.0 mm or less and 4.0 mm or less. The inner radius of the teeth 3 means the radial dimension from the axial center of the back yoke 2 to the surface positioned on the inner peripheral side of the teeth 3 . The inner radius of the back yoke 2 means the radial dimension from the axial center of the back yoke 2 to the inner peripheral surface. In FIG. 1, the inner radius of the teeth 3 is indicated by R3i, and the inner radius of the back yoke 2 is indicated by R2i. When the difference (R3i−R2i) between the inner radius of the teeth 3 and the inner radius of the back yoke 2 is 7.0 mm or less, the radial dimension of the inner peripheral region 28 of the back yoke 2 is reduced as shown in FIG. becomes smaller. The inner peripheral region 28 of the back yoke 2 refers to the region from the inner peripheral surface of the back yoke 2 to the portion where the teeth 3 protrude. As the radial dimension of the inner peripheral region 28 of the back yoke 2 is smaller, the bending stress acting on the inner peripheral region 28 when removing the molded core 1 from the mold can be reduced. The reason for this will be described later. Therefore, if the difference between the inner radius R3i of the teeth 3 and the inner radius R2i of the back yoke 2 is 7.0 mm or less, and further 5.0 mm or less, the deformation of the inner peripheral region 28 due to stress during removal from the mold can be prevented. can be suppressed.

Further, when the difference between the inner radius R3i of the teeth 3 and the inner radius R2i of the back yoke 2 is 7.0 mm or less, and further 4.0 mm or less, the compression area when molding the core using a mold becomes small. . Therefore, since high molding pressure can be applied, the density of the core 1 can be increased. The reason for this will be described later.

Among the plurality of teeth 3 in the core 1, the difference between the position of the end face of the highest tooth 3 and the position of the end face of the lowest tooth 3 is preferably 0.2 mm or less, for example. The positions of the end surfaces of the teeth 3 are, as shown in FIG. It means the position H3. Since the difference between the position of the end face of the highest tooth 3 and the position of the end face of the lowest tooth 3 is 0.2 mm or less, variations in the height of each end face of the teeth 3 are small. As will be described later, when rotating electric machine 300 shown in FIG. 12 is configured using core 1 , each end face of teeth 3 is arranged to face magnet 220 of rotor 200 . Since the variation in the height of each end surface of teeth 3 is small, variation in the distance between each end surface of teeth 3 and rotor 200 can be reduced in rotary electric machine 300 . As a result, deterioration of the characteristics of rotating electric machine 300 can be suppressed, for example, cogging can be reduced.

(Compact compact)
The back yoke 2 and the teeth 3 are integrally formed from powder compacts. That is, the core 1 is composed of a compacted body. A powder compact is formed by compressing soft magnetic powder. A soft magnetic powder is an aggregate of a plurality of coated soft magnetic particles having an insulating coating on the surface of the soft magnetic particles. That is, the powder compact is composed of an aggregate of a plurality of coated soft magnetic particles. In this example, the powder compact that constitutes the core 1 is substantially composed only of the soft magnetic powder composed of the coated soft magnetic particles.

The soft magnetic particles are, for example, pure iron with a purity of 99% by mass or more, Fe (iron)-Si (silicon) alloy, Fe (iron)-Al (aluminum) alloy, Fe (iron)-Cr (chromium )-Al (aluminum) alloys and Fe (iron)-Cr (chromium)-Si (silicon) alloys. Pure iron or the above iron-based alloys are relatively soft. Therefore, when the soft magnetic particles are iron-based particles made of pure iron or the iron-based alloy, the soft magnetic particles are easily deformed during molding of the powder compact forming the core 1 . Therefore, a powder compact having a high density and high dimensional accuracy can be obtained. The mechanical strength and magnetic properties of the core 1 can be improved by increasing the density of the powder compact. Moreover, by having an insulating coating on the surface of the soft magnetic particles, the electrical insulation between the soft magnetic particles can be enhanced. Therefore, iron loss of the core 1 caused by eddy current loss can be reduced. Examples of insulating coatings include phosphate coatings and silica coatings. Among others, the insulating coating preferably includes a phosphate coating. Phosphate coating has high adhesion to iron-based particles and is excellent in deformability. Therefore, since the insulating coating contains the phosphate coating, it is easy to follow the deformation of the iron-based particles during the molding of the powder compact. Therefore, the insulation coating is less likely to be damaged, and the iron loss of the core 1 can be reduced.

The relative density of the powder compact forming the core 1 is preferably 90% or more. The mechanical strength and magnetic properties of the core 1 can be improved by increasing the density of the powder compact. A more preferable relative density is 93% or more. The relative density is the ratio (%) of the actual density of the compact to the true density of the compact. The true density of the powder compact can be obtained from the true density of the soft magnetic powder. The relative density of the powder compact can be obtained, for example, by [(molding density of the compact/true density of the compact)×100]. The compacting density of the green compact is obtained by immersing the green compact in oil and impregnating the green compact with oil, [oil-impregnated density × (mass of green compact before oil impregnation / compaction after oil impregnation It can be obtained from the mass of the molded body)]. The oil-impregnated density is a value obtained by dividing the mass of the powder compact after impregnating oil by the volume. The volume of the compact can typically be measured by a liquid displacement method.

<Mold>
The core 1 made of a powder compact can be manufactured by compressing and molding soft magnetic powder with a mold. The mold 5 used for manufacturing the core 1 will be described below with reference to FIGS. 4 to 10. FIG. The mold 5 includes a die 50 , a core rod 60 arranged in the die 50 , and upper and lower punches 70 and 80 fitted to the die 50 , as shown in FIG. 4 .

Die 50 is a stepped die. The die 50 includes a first molding portion 51 and a plurality of second molding portions 52, as shown in FIGS. have The first forming portion 51 is a portion that forms a space for forming the back yoke 2 shown in FIGS. 1 and 2 . The second forming portion 52 is a portion that forms a space for forming the teeth 3 shown in FIGS. 1 and 2 . The first forming part 51 is provided above the die 50 . The second molding portion 52 is provided below the die 50 so as to be continuous with the first molding portion 51 . A core rod 60 is coaxially disposed within the first forming portion 51 of the die 50 . The upper punch 70 is positioned above the die 50 and fitted to the first forming portion 51 from above. The lower punch 80 is positioned below the die 50 and fitted to the second forming portion 52 from below. The lower punch 80 has, as shown in FIGS. 8 and 9, a plurality of punch portions 82 inserted into the second forming portion 52 shown in FIGS. 5 and 6 on its distal end side. The base end side of the punch portion 82 is integrally formed.

In the mold 5 shown in FIG. 4, the first molding portion 51 of the die 50, the core rod 60 and the upper punch 70 form an annular space for molding the back yoke 2 shown in FIGS. A columnar space for forming the teeth 3 shown in FIGS. 1 and 2 is formed by the second forming portion 52 of the die 50 and the punch portion 82 of the lower punch 80 . When molding the core 1 using the mold 5, the core rod 60 was arranged in the first molding portion 51 of the die 50, and the punch portions 82 of the lower punch 80 were inserted into the respective second molding portions 52. state. In this state, the first molding portion 51 and the second molding portion 52 are filled with raw material powder (not shown). Then, the upper punch 70 is lowered, and the raw material powder is pressed by the upper punch 70 from above the first forming portion 51 . As shown in FIG. 10 , when the core 1 is formed using the mold 5 , the inner peripheral surface of the first forming portion 51 forms the outer peripheral surface of the back yoke 2 , and the surface of the stepped portion 53 forms the outer peripheral surface of the back yoke 2 . The first plane 21 is molded. The outer peripheral surface of the core rod 60 forms the inner peripheral surface of the back yoke 2 . The end face of the upper punch 70 forms the second plane 22 of the back yoke 2 . In addition, the inner peripheral surface of the second forming portion 52 forms the peripheral surface of the tooth 3 . The end face of the tooth 3 is formed by the end face of the punch portion 82 of the lower punch 80 . On the other hand, when removing the molded core 1 from the mold 5 , the upper punch 70 is raised and the die 50 and core rod 60 are lowered with respect to the lower punch 80 . Then, the core 1 is extracted from the die 50 while supporting the end faces of the teeth 3 with the punch portion 82 .

The raw material powder contains soft magnetic powder as a main component. The main component means that it contains 90% by mass or more when the raw material powder is taken as 100% by mass. A lubricant, a binder resin, or the like may be added to the raw material powder as necessary.

The average particle size of the soft magnetic powder is, for example, 20 μm or more and 300 μm or less, and more preferably 40 μm or more and 250 μm or less. By setting the average particle size of the soft magnetic powder within the above range, it is easy to handle and compact. The average particle size of the soft magnetic powder is measured using a laser diffraction/scattering particle size/particle size distribution analyzer, and means the particle size at which the accumulated mass is 50% of the mass of all particles.

The density of the core 1 can be increased by increasing the molding pressure when compressing the raw material powder containing the soft magnetic powder. The molding pressure is, for example, 700 MPa or higher, and more preferably 800 MPa or higher.

As shown in FIG. 7, in the die 50, a first corner portion 531 between the surface of the stepped portion 53 and the inner peripheral surface of the second forming portion 52 is aligned with the first curved surface portion 31 of the core 1 shown in FIG. Corresponding curved surfaces are formed. The curvature radius of the first corner portion 531 is 0.2 mm or more and 1.5 mm or less. Since the first corner portion 531 is formed in a curved shape, the first curved portion 31 is formed at the corner portion between the teeth 3 and the back yoke 2 .

Further, as shown in FIG. 7, an outer edge corner portion 532 and an inner edge corner portion 533 of the stepped portion 53 are formed in a curved surface shape corresponding to the outer curved surface portion 23 and the inner curved surface portion 24 of the back yoke 2 shown in FIG. there is Each curvature radius of the outer edge corner portion 532 and the inner edge corner portion 533 is, for example, 0.5 mm or more and 5.0 mm or less. Since the outer edge corner portion 532 and the inner edge corner portion 533 are formed in a curved surface shape, the outer curved surface portion 23 and the inner curved surface portion 24 are formed at the corner portions of the outer peripheral edge and the inner peripheral edge of the back yoke 2 .

When the raw material powder is pressed by the upper punch 70 to form the core 1, the second flat surface 22 of the back yoke 2 pressed by the end surface of the upper punch 70 becomes a compression surface, as shown in FIG. At this time, the surface of the stepped portion 53 and the end surface of the punch portion 82 of the lower punch 80 serve as pressure receiving surfaces. In this case, since the pressure acting on the surface of the step portion 53 is received by the outer edge corner portion 532 and the inner edge corner portion 533 , the bending stress tends to concentrate on the outer edge corner portion 532 and the inner edge corner portion 533 . Stress concentration can be relieved by setting the radius of curvature of each of the outer edge corner portion 532 and the inner edge corner portion 533 to be 0.5 mm or more. Therefore, damage to the die 50 can be suppressed.

On the other hand, when the molded core 1 is removed from the mold 5, only the end surfaces of the teeth 3 are supported by the punch portion 82, and the die 50 is lowered so that the core 1 is relatively pushed up. At this time, the outer peripheral surface of the back yoke 2 slides on the inner peripheral surface of the first molded portion 51 . Also, the inner peripheral surface of the back yoke 2 slides on the outer peripheral surface of the core rod 60 . Therefore, bending stress acts on the outer peripheral region 27 and the inner peripheral region 28 of the back yoke 2 projecting radially outward and inward from the teeth 3 shown in FIG. Since the difference between the outer radius R2o of the back yoke 2 and the outer radius R3o of the teeth 3 shown in FIG. 1 is 6.0 mm or less, the radial dimension of the outer peripheral region 27 is reduced. Further, since the difference between the inner radius R3i of the teeth 3 and the inner radius R2i of the back yoke 2 shown in FIG. 1 is 7.0 mm or less, the radial dimension of the inner peripheral region 28 is reduced. Therefore, when the core 1 is removed from the mold 5, the bending stress acting on the outer peripheral region 27 and the inner peripheral region 28 can be reduced, so that the deformation of the outer peripheral region 27 and the inner peripheral region 28 can be suppressed.

One of the difference between the outer radius R2o of the back yoke 2 and the outer radius R3o of the teeth 3, and the difference between the inner radius R3i of the teeth 3 and the inner radius R2i of the back yoke 2, preferably both are 4.0 mm or less, further 3 0 mm or less, the area of the second plane 22 can be reduced. When molding the core 1 with the die 5, as shown in FIG. 10, the smaller the area of the second plane 22, the smaller the area of the compression surface pressed by the end surface of the upper punch 70. As shown in FIG. Since the compressed area is small, a high molding pressure can be applied, so that the core 1 can be densified. The difference between the outer radius R2o of the back yoke 2 and the outer radius R3o of the teeth 3 and the difference between the inner radius R3i of the teeth 3 and the inner radius R2i of the back yoke 2 may be the same or different. good. 1 and 2 illustrate the case where the difference between the outer radius R2o of the back yoke 2 and the outer radius R3o of the teeth 3 is greater than the difference between the inner radius R3i of the teeth 3 and the inner radius R2i of the back yoke 2. ing. When the core 1 is molded, the inner peripheral side of the back yoke 2 and the teeth 3 has less springback and less friction with the mold 5. - 特許庁Therefore, the load applied to the root portion of the tooth 3 is smaller on the inner peripheral side. Therefore, the difference between the inner radius R3i of the teeth 3 and the inner radius R2i of the back yoke 2 can be made larger than the difference between the outer radius R2o of the back yoke 2 and the outer radius R3o of the teeth 3 .

<Stator>
A stator 100 according to the embodiment will be described with reference to FIG. 11 . Stator 100 is used in an axial gap type rotating electric machine. Stator 100 includes core 1 and coils 110 arranged on teeth 3 of core 1 . Coil 110 is configured by winding a wire around teeth 3 .

<Rotating electric machine>
A rotating electric machine 300 according to the embodiment will be described with reference to FIG. 12 . Rotating electric machine 300 may be a motor or a generator. Rotating electric machine 300 includes a rotor 200 and a stator 100 . The rotating electrical machine 300 is an axial gap type rotating electrical machine in which a rotor 200 and a stator 100 are arranged to face each other in the direction of the rotation axis.

Stator 100 and rotor 200 are housed in cylindrical case 310 . Disc-shaped plates 320 are attached to both ends of the case 310 . A through hole is formed in the center of both plates 320 , and a rotating shaft 330 passes through the case 310 .

(rotor)
The rotor 200 includes a plurality of plate-shaped magnets 220 and an annular holding plate 210 that supports the magnets 220 . The planar shape of the magnet 220 is a shape substantially corresponding to the end face of the tooth 3 . When the shape of the end surface of the tooth 3 is triangular, the planar shape of the magnet 220 may be, for example, triangular or trapezoidal. The holding plate 210 is fixed to the rotating shaft 330 and rotates together with the rotating shaft 330 . Each magnet 220 is embedded in the holding plate 210 . Each magnet 220 may be fixed to the retaining plate 210 with an adhesive. The magnets 220 are arranged at regular intervals in the circumferential direction of the rotating shaft 330 . Also, the magnet 220 is magnetized in the axial direction of the rotating shaft 330 . The magnetization directions of the magnets 220 adjacent in the circumferential direction are opposite to each other.

(stator)
Stator 100 is arranged such that the end surfaces of teeth 3 face magnets 220 of rotor 200 . Stator 100 is fixed to case 310 by fitting the outer peripheral surface of back yoke 2 of core 1 to the inner peripheral surface of case 310 . In this example, since the outer peripheral surface of the back yoke 2 has the linear portion 25 , it is easy to fix the core 1 constituting the stator 100 to the case 310 . An annular bearing 340 that rotatably supports the rotary shaft 330 is arranged on the inner peripheral side of the back yoke 2 .

[Modification]
In the core 1, at least one of the outer peripheral surface and the inner peripheral surface of the back yoke 2 may have protrusions or recesses. 13A and 13B, 14A and 14B, an example in which the outer peripheral surface of the back yoke 2 has a convex portion 41 or a concave portion 42 will be described.

The core 1 shown in FIG. 13A has a convex portion 41 that protrudes radially from the outer peripheral surface of the back yoke 2 . The convex portion 41 is partially provided on the outer peripheral surface of the back yoke 2 . Although the example shown in FIG. 13A shows the case where the number of protrusions 41 is one, the number of protrusions 41 may be plural. In this example, the shape of the convex portion 41 when the core 1 is viewed from above is rectangular. The shape of the convex portion 41 is not limited to a rectangular shape, and may be, for example, a semicircular shape, a triangular shape, a trapezoidal shape, or the like.

When the rotating electrical machine 300 is constructed using the core 1 shown in FIG. 13A, as shown in FIG. . It is possible to position the core 1 of the stator 100 with respect to the case 310 by fitting the protrusions 41 and the recesses 311 .

The core 1 shown in FIG. 14A has a recess 42 that is recessed in the radial direction on the outer peripheral surface of the back yoke 2 . The recess 42 is partially provided on the outer peripheral surface of the back yoke 2 . Although the example shown in FIG. 14A shows the case where there is one recess 42, the number of recesses 42 may be plural. In this example, the recess 42 has a rectangular shape when the core 1 is viewed from above. The shape of the recess 42 is not limited to a rectangular shape, and may be semicircular, triangular, or trapezoidal, for example.

When the rotating electric machine 300 is configured using the core 1 shown in FIG. 14A, as shown in FIG. . It is possible to position the core 1 of the stator 100 with respect to the case 310 by fitting the concave portion 42 and the convex portion 312 together.

13A and 13B and FIGS. 14A and 14B illustrate examples in which the outer peripheral surface of the back yoke 2 has the protrusions 41 or the recesses 42. may be provided. The number of protrusions or recesses is not particularly limited as long as it is one or more. The shape of the protrusions or recesses when the core 1 is viewed in plan may be rectangular, semicircular, triangular, or trapezoidal, for example.

For example, a bus bar (not shown) may be arranged inside the back yoke 2 . In that case, a convex portion or a concave portion is provided on the inner peripheral surface of the back yoke 2, and a concave portion or a convex portion corresponding to the convex portion or the concave portion is provided on the outer peripheral surface of the bus bar. It is possible to position the busbar with respect to the core 1 by fitting these protrusions and recesses.

As described above, since at least one of the outer peripheral surface and the inner peripheral surface of the back yoke 2 has a protrusion or a recess, the protrusion or recess can be used for positioning. Moreover, when using a convex portion or a concave portion for positioning, the shape of the convex portion or concave portion when the core 1 is viewed from above preferably has at least one linear portion. A linear portion is a portion of the outline of a convex portion or a concave portion when the core 1 is viewed from above, which is composed of straight lines. Positioning accuracy can be improved by having a straight portion in the shape of the convex portion or the concave portion.

{Effect of embodiment}
The core 1, the stator 100, and the rotating electric machine 300 of the embodiment described above have the following effects.

The core 1 has a first curved surface portion having a radius of curvature of 0.2 mm or more at the corners between the teeth 3 and the back yoke 2, so that leakage magnetic flux generated at the corners between the teeth 3 and the back yoke 2 can be reduced. . Therefore, loss due to leakage magnetic flux can be suppressed. Moreover, since the radius of curvature of the first curved surface portion 31 is 1.5 mm or less, it is possible to suppress a decrease in the number of turns of the coil 110 . As a result, reduction in the torque of rotating electric machine 300 can be suppressed.

Since the stator 100 includes the core 1, it has excellent magnetic properties. Rotating electric machine 300 is highly efficient by including stator 100 .

[Test Example 1]
A core having the same configuration as the core 1 described in the embodiment was produced and evaluated. In Test Example 1, a plurality of cores having first curved surface portions 31 with different radii of curvature were prepared. Sample no. 1-0 to No. 1-6. A stator 100 was produced by winding a wire around each tooth 3 of the prepared core 1 to form a coil 110 . Then, using the manufactured stator 100, an axial gap type rotating electric machine 300 was constructed. This rotating electric machine 300 functions as a motor.

A copper wire with a wire diameter of 1.5 mm was used for the winding. Table 1 shows the number of coil turns in each sample.

Using electromagnetic field analysis software, the magnetic flux density distribution of the core was analyzed when current was passed through the coil, and the maximum magnetic flux density at the root of the teeth was obtained. The electromagnetic field analysis software used is "JMAG" manufactured by JSOL. Table 1 shows the maximum magnetic flux density at the root of each sample. Also, the iron loss of the core and the torque of the motor were determined by electromagnetic field analysis. The results are also shown in Table 1.

From Table 1, it can be seen that sample No. 1 in which the radius of curvature of the first curved surface portion is 0.2 mm or more. 1-1 to No. Sample No. 1-6 has a radius of curvature of 0 mm. It can be seen that the iron loss is smaller than that of 1-0. Sample No. having a radius of curvature of 0 mm. In 1-0, it is considered that iron loss due to leakage magnetic flux increased due to magnetic flux short-circuiting between the circumferential surface of the teeth and the first plane of the back yoke. On the other hand, sample no. 1-1 to No. In 1-6, since the radius of curvature is 0.2 mm or more, it is considered that the short-cut leakage magnetic flux is reduced and the iron loss due to the leakage magnetic flux is reduced.

Sample no. 1-1 to No. From the comparison of 1-6, it can be seen that the larger the radius of curvature of the first curved surface portion, the more the iron loss can be suppressed. However, sample No. with a curvature radius of 2.0 mm. Sample No. 1-6 has a radius of curvature of 1.5 mm or less. 1-1 to No. It can be seen that the torque is reduced compared to 1-5. This is sample no. Sample No. 1-6 has a large radius of curvature. 1-1 to No. This is because the number of turns of the coil is reduced compared to 1-5.

From the above, it can be said that the radius of curvature of the first curved surface portion is preferably 0.2 mm or more and 1.5 mm or less.

[Test Example 2]
The stress distribution acting on the die 50 when the core 1 described in the embodiment was molded by the mold 5 was analyzed by CAE (Computer Aided Engineering). Then, the maximum stress generated in the outer edge corner portion 532 of the stepped portion 53 in the die 50 was obtained from the result of stress analysis by CAE. In Test Example 2, the radius of curvature of the outer edge corner portion 532 was varied, and the maximum stress was obtained in each case. Table 2 shows the results.

Structural analysis software, specifically "NX Nastran" manufactured by Siemens, was used for the stress analysis. The analysis conditions were set as follows. The molding pressure was 980 MPa. The physical properties of the die 50 were Young's modulus: 206000 MPa and Poisson's ratio: 0.3. The back yoke 2 of the core 1 to be molded has an outer radius R2o of 25 mm, an inner radius R2i of 10 mm, and a thickness T2 of 3.0 mm.

From Table 2, it can be seen that the larger the radius of curvature of the outer edge corners, the more the maximum stress at the outer edge corners during core molding can be reduced. In particular, when the radius of curvature of the outer edge corner is 0.5 mm or more, the maximum stress generated at the outer edge corner can be reduced to 2000 MPa or less.

Since the curved surface of the outer edge corner portion of the stepped portion of the die is a portion for forming the outer curved surface portion of the back yoke of the core, it can be said that the radius of curvature of the outer curved surface portion is preferably 0.5 mm or more.

[Test Example 3]
In Test Example 3, as in Test Example 2, the maximum stress generated in the inner edge corner portion 533 of the stepped portion 53 in the die 50 during core molding was determined by CAE stress analysis. Table 3 shows the results. Analysis conditions are the same as in Test Example 2.

From Table 3, it can be seen that the larger the radius of curvature of the inner edge corners, the more the maximum stress at the inner edge corners during core molding can be reduced. In particular, when the radius of curvature of the inner edge corner is 0.5 mm or more, the maximum stress generated in the inner edge corner can be reduced to 2000 MPa or less, and further to 1500 MPa or less.

Since the curved surface of the inner edge corner portion of the stepped portion of the die is a portion for forming the inner curved surface portion of the back yoke of the core, it can be said that the radius of curvature of the inner curved surface portion is preferably 0.5 mm or more. Further, from the results in Tables 2 and 3, it can be seen that the maximum stress during core molding tends to be higher at the outer edge corners of the stepped portion of the die than at the inner edge corners. Therefore, it is preferable to make the radius of curvature of the outer corner portion larger than the radius of curvature of the inner corner portion, that is, make the radius of curvature of the outer curved surface portion larger than that of the inner curved surface portion. In view of the fact that the magnetic flux flowing through the back yoke tends to selectively pass through the inner peripheral side, it is preferable to make the radius of curvature of the outer curved surface portion larger than the radius of curvature of the inner curved surface portion also from the viewpoint of motor performance. .

The following notes are further disclosed in relation to the embodiments of the present disclosure described above.

[Appendix 1]
A core used in an axial gap type rotating electric machine,
an annular back yoke;
a plurality of teeth projecting axially from the first plane of the back yoke,
The plurality of teeth are provided at intervals in the circumferential direction of the first plane,
The back yoke and the teeth are formed of an integrally molded compacted body,
a first curved surface portion connecting between the peripheral surface of the tooth and the first flat surface of the back yoke at a corner portion between the tooth and the back yoke;
The curvature radius of the first curved surface portion is 0.2 mm or more and 1.5 mm or less,
core.

The core according to Supplementary Note 1 has the first curved surface portions at the corners of the teeth and the back yoke, so that leakage magnetic flux generated at the corners of the teeth and the back yoke can be reduced. Therefore, the core of Supplementary Note 1 can improve the magnetic properties. Leakage magnetic flux can be effectively reduced by setting the radius of curvature of the first curved surface portion to 0.2 mm or more. In addition, since the radius of curvature of the first curved surface portion is 1.5 mm or less, it is possible to secure space for the coils arranged on the teeth and improve the space factor of the coils. As a result, a decrease in the number of turns of the coil can be suppressed, so a decrease in the torque of the rotating electric machine can be suppressed.

[Appendix 2]
an outer curved surface portion connecting between the first plane and the outer peripheral surface of the back yoke;
an inner curved surface portion connecting between the first plane and the inner peripheral surface of the back yoke,
The core according to appendix 1, wherein the radius of curvature of each of the outer curved surface portion and the inner curved surface portion is 0.5 mm or more and 5.0 mm or less.

The core made of the powder compact is formed by compressing the soft magnetic powder with a mold. When molding a core using a mold, bending stress tends to concentrate on the corners of the mold, particularly the die, and cracks may occur in the corners of the mold. In the form of Supplementary Note 2, the radius of curvature of each of the outer curved surface portion and the inner curved surface portion of the back yoke is 0.5 mm or more, so that stress concentration at the corners of the mold can be alleviated. Therefore, the above configuration can suppress damage to the mold. As the radius of curvature of each of the outer curved surface portion and the inner curved surface portion increases, the length of the straight portions of the outer peripheral surface and the inner peripheral surface of the back yoke becomes shorter than the thickness of the back yoke. If the radius of curvature of each of the outer curved surface portion and the inner curved surface portion is 5.0 mm or less, it is easy to secure large lengths of the straight portions of the outer peripheral surface and the inner peripheral surface of the back yoke.

[Appendix 3]
The powder compact is composed of an aggregate of a plurality of coated soft magnetic particles having an insulating coating on the surface of the soft magnetic particles,
The core according to appendix 1, wherein the soft magnetic particles have an average particle size of 20 μm or more and 300 μm or less.

The average particle size of the soft magnetic particles forming the powder compact depends on the average particle size of the soft magnetic powder contained in the raw material powder. When the average particle size of the soft magnetic particles is 20 μm or more and 300 μm or less, it is easy to obtain a dense and high-density powder compact.

The average particle size of the soft magnetic particles in the compact can be obtained as follows.
Any cross section of the compact is observed with a microscope such as a scanning electron microscope (SEM) or an optical microscope. All soft magnetic particles existing within the observation field are extracted and the area of each particle is measured. The diameter of each circle having an area equal to the area of each particle is calculated, and the average value is taken as the average particle diameter of the soft magnetic particles. The size of the observation field is set so as to include, for example, 50 or more soft magnetic particles. Image analysis software or the like may be used to extract the soft magnetic particles, measure the area, and calculate the equivalent circle diameter of equal area.

[Appendix 4]
The powder compact is composed of an aggregate of a plurality of coated soft magnetic particles having an insulating coating on the surface of the soft magnetic particles,
The core according to appendix 1, wherein the soft magnetic particles have an average particle size of 40 μm or more and 250 μm or less.

When the average particle size of the soft magnetic particles is 40 μm or more and 250 μm or less, it is easy to obtain a more dense and high-density powder compact.

[Appendix 5]
The core according to appendix 1, wherein the compact has a relative density of 93% or more.

When the relative density of the powder compact is 93% or more, the density of the powder compact is high. By increasing the density of the powder compact, the mechanical strength and magnetic properties of the core can be improved.

1 core 2 back yoke 21 first plane 22 second plane 23 outer curved surface 24 inner curved surface 25, 26 straight portion 27 outer peripheral area 28 inner peripheral area 3 tooth 31 first curved surface 41 convex 42 concave 5 mold 50 die 51 first formed portion 52 second formed portion 53 step portion 531 first corner portion 532 outer edge corner portion 533 inner edge corner portion 60 core rod 70 upper punch 80 lower punch 82 punch portion 100 stator 110 coil 200 rotor 210 holding plate 220 magnet 300 rotation Electric machine 310 Case 311 Concave part 312 Protruding part 320 Plate 330 Rotating shaft 340 Bearing T2 Thickness R2o, R3o Outer radius R3i, R2i Inner radius H3 Height position

Claims (13)

A core used in an axial gap type rotating electric machine,
an annular back yoke;
a plurality of teeth protruding in an axial direction perpendicular to the first plane of the back yoke,
the back yoke has a second plane opposite to the first plane,
The plurality of teeth are provided at intervals in the circumferential direction of the first plane,
The back yoke and the teeth are formed of an integrally molded compacted body,
a first curved surface portion connecting between the peripheral surface of the tooth and the first flat surface of the back yoke at a corner portion between the tooth and the back yoke;
the distance between the first curved surface portion and the second plane increases from the first plane toward the peripheral surface of the tooth,
The curvature radius of the first curved surface portion is 0.2 mm or more and 1.5 mm or less,
core. an outer curved surface portion connecting between the first plane and the outer peripheral surface of the back yoke;
an inner curved surface portion connecting between the first plane and the inner peripheral surface of the back yoke,
2. The core according to claim 1, wherein each radius of curvature of said outer curved surface portion and said inner curved surface portion is 0.5 mm or more. 3. The core according to claim 2, wherein the curvature radius of the outer curved surface portion and the curvature radius of the inner curved surface portion are different. At least one of the outer peripheral surface and the inner peripheral surface of the back yoke has a linear portion extending along the axial direction,
4. The core according to any one of claims 1 to 3, wherein the length of said straight portion is 15% or more of the thickness of said back yoke. The difference between the radial dimension from the axial center of the back yoke to the outer peripheral surface and the radial dimension from the axial center of the back yoke to the outer peripheral surface of the tooth is 6.0 mm or less. A core according to any one of claims 1 to 4. The difference between the radial dimension from the axial center of the back yoke to the surface positioned on the inner peripheral side of the tooth and the radial dimension from the axial center to the inner peripheral surface of the back yoke is 7.0 mm or less. A core according to any one of claims 1 to 5. 7. The back yoke according to any one of claims 1 to 6, wherein at least one of the outer peripheral surface and the inner peripheral surface of the back yoke is partially provided with a radially projecting projection or a radially recessed recess. core. The powder compact is composed of an aggregate of a plurality of coated soft magnetic particles having an insulating coating on the surface of the soft magnetic particles,
The soft magnetic particles are made of pure iron or at least one iron-based alloy selected from Fe—Si alloys, Fe—Al alloys, Fe—Cr—Al alloys and Fe—Cr—Si alloys. 8. The core according to any one of claims 1 to 7, which is an iron-based particle. 9. The core of claim 8, wherein said insulating coating comprises a phosphate coating. 10. The core according to any one of claims 1 to 9, wherein the green compact has a relative density of 90% or more. A core used in an axial gap type rotating electric machine,
an annular back yoke;
a plurality of teeth protruding in an axial direction perpendicular to the first plane of the back yoke,
the back yoke has a second plane opposite to the first plane,
The plurality of teeth are provided at intervals in the circumferential direction of the first plane,
The back yoke and the teeth are formed of an integrally molded compacted body,
a first curved surface portion connecting between the peripheral surface of the tooth and the first flat surface of the back yoke at a corner portion between the tooth and the back yoke;
the distance between the first curved surface portion and the second plane increases from the first plane toward the peripheral surface of the tooth,
The first curved surface portion has a radius of curvature of 0.2 mm or more and 1.5 mm or less,
an outer curved surface portion connecting between the first plane and the outer peripheral surface of the back yoke;
an inner curved surface portion connecting between the first plane and the inner peripheral surface of the back yoke,
Each curvature radius of the outer curved surface portion and the inner curved surface portion is 0.5 mm or more,
At least one of the outer peripheral surface and the inner peripheral surface of the back yoke has a linear portion extending along the axial direction,
the length of the straight portion is 15% or more of the thickness of the back yoke,
core. A stator for an axial gap type rotary electric machine,
a core according to any one of claims 1 to 11;
a coil arranged on each tooth of the core,
stator. An axial gap type rotary electric machine comprising a rotor and a stator, wherein the rotor and the stator are arranged to face each other in an axial direction,
wherein the stator is the stator of claim 12,
rotating electric machine.

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